Researchers from Dartmouth College, National Taiwan University, and the University of Science and Technology of China have developed a new kind of thread with sensing capabilities that can be incorporated into braids, tinsels, embroidery, and more. Known as ThreadSense, the interactive thread is made from a conductive material that uses impedance sensing to register up to two inputs at the same time, which the team states works on cords, stripes, and very thin threads.
According to a recently published paper, the researchers employ a new method for sensing inputs by locating touches using a mathematical model that describes the changes in impedance of the thread in relation to the touch. Unlike other impedance platforms, ThreadSense doesn't need to be trained, but rather the user performs a quick calibration by touching known locations on the thread, which informs the system of their finger impedance.
ThreadSense was designed using an Ultimaker 3 3D printer to extrude a thin line off conductive filament thermally and coupled it with a 470kΩ resistor to extend the sensing range through the length of the sensor. The ends of the interactive thread are connected to an AD5933 impedance sensing board, which is outfitted with a 1Msps ADC (Analog to Digital) converter, and a DSP (Digital Signal Processor) that measures the frequency along the thread.
The sensor data is then sent to a Macbook Pro via USB to compute the touch locations, which takes on average of 25 to 26ms to locate single and double touches, respectively. To test ThreadSense, the researchers created several projects using the interactive thread, including an embroidered cushion cover of an owl. When touched at different locations, the owl can activate/deactivate Amazon's Alexa, play music, or listen to the news like an always-on remote control. Another example is a braided headband that enables gestural smartphone input to be carried out as if the user is scratching their hair.
The team envisions that TouchSense could go beyond 1D touch sensing and could pave the way to further techniques for interactive touch on flat thin surfaces.